The present invention relates to a liquid ejecting apparatus which ejects a liquid supplied from a liquid cartridge or the like as liquid droplets, and particularly to a liquid ejecting apparatus equipped with an ejecting head position adjustment mechanism.
As one kind of liquid ejecting apparatus, there is an inkjet recording apparatus. Such an inkjet recording apparatus has an advantage that it is possible to print directly on a recording medium and, what is more, it is easy to reduce the size of a head, and furthermore that a color printing can easily be carried out by changing ink colors. However, in the event that a plurality of inkjet heads or printhead cartridges are mounted on an identical carriage, due to a mechanical tolerance which each head has and an attaching tolerance, relative positions of nozzles are deviated relative to their ideal positions, whereby a satisfactory printing quality cannot be obtained.
Particularly, in a printhead cartridge having an ink cartridge and a head integrally configured, since a head is also replaced when an ink is ran out, it is necessary to adjust the heads each time. However, since it is not possible to force a user to work on the adjustment, a result of a test printing is read by a sensor, and a cam is driven by an actuator to adjust the relative positions of the heads. However, this adjustment method has a problem in which it naturally leads to a complicated configuration and an adjustment operation is necessitated on each occasion of head replacement.
At this point, as an inkjet recording apparatus equipped with a head position adjustment mechanism, ones shown in JP-A-7-314851 and JP-A-2002-19097 are disclosed.
The apparatus shown in JP-A-7-314851 is one which is configured to be able to adjust the relative positions of two recording heads, in which positioning of the two recording heads in a scanning direction is carried out by engaging them in respective head guide grooves of a carriage, while positioning of the recording heads in a paper feed direction is carried out by bringing them in close with a head positioning surface by means of a spring. Furthermore, an adjustment plate is attached to one of the recording heads with reference to the other recording head, thereby adjusting a deviation of the two recording heads from each other.
The apparatus shown in JP-A-2002-19097 includes: a nozzle unit which has a plurality of nozzles; a sub-carriage on which a plurality of the nozzle units can be integrally fixed; and a carriage which has the sub-carriage mounted thereon and can slide in a main scanning direction, in which a cam mechanism is adopted as a tilt adjustment section which adjusts a tilt of the sub-carriage in a yawing direction with respect to the main scanning direction.
In order to realize a high-speed printing, an increase in the number of nozzles of a head unit has been considered. In such a head unit, one unit head is configured by arranging a plurality of unit heads.
FIG. 12 shows an example of a head unit 60 configured by arranging a plurality of ejecting heads 61. In this example, a configuration is such that two ejecting heads 61 including four nozzle arrays 62 are arranged in a main scanning direction X. Such a head unit 60, being mounted on a not-shown carriage, reciprocates in the main scanning direction X, and ejects ink droplets from nozzles configuring each nozzle array 62 while feeding a recording medium toward a sub-scanning direction Y, thereby forming an image on the recording medium using a dot matrix. Consequently, it is necessary that the plurality of ejecting heads 61 are accurately positioned.
Regarding the relative positions of the two ejecting heads 61, since a deviation in the X direction can be electrically corrected by a method such as delaying an ejection timing, no practical issue arises even in the event that an adjustment of accuracy is not so strictly carried out. However, as a deviation in the Y direction, which is a paper feed direction, cannot be electrically corrected, physical attachment positions need to be aligned with high accuracy. In such a Y direction positioning, it is necessary that (1) the ejecting heads 61 are aligned so that a Y direction tilt of the nozzle arrays 62 is made parallel to the Y direction, and thereafter (2) the ejecting heads 61 are adjusted with respect to each other as to their absolute position accuracy in the Y direction.
In the related art described heretofore, regarding both a tilt of nozzle arrays and an absolute position of an ejecting head, such as described heretofore, a highly accurate positioning cannot be realized by a simple structure and operation.